To investigate the protective effect and mechanism of astragaloside Ⅳ (AS-Ⅳ) on intestinal injury and secondary liver injury in rats with ulcerative colitis (UC) induced by trinitrobenzene sulfonic acid (TNBS).

Wistar rats were randomly divided into normal control group, UC model group and AS-Ⅳ experimental low, medium and high dose groups, with 10 rats in each group. The UC rat model was prepared by TNBS enema. AS-Ⅳ (25, 50, 100 mg·kg^-1) or sulfasalazine (SASP, 300 mg·kg^-1) was administered intragastrically for 6 consecutive days starting from the second day after modeling. The general condition, colonic histopathological score, and liver function of the rats were examined. The levels of inflammatory factors in serum, colon and liver tissues were detected by enzyme-linked immunosorbent assay (ELISA). The expressions of tight junction proteins (ZO-1, Occludin) in colon and antioxidant enzymes in liver tissues were detected by Western blot.

In the normal group, model group, low, medium and high dose experimental groups, the serum TNF-α levels were (246.30±23.39), (308.70±61.39), (279.10±45.76), (240.80±16.61) and (233.60±30.14) pg·mL^-1, and the serum IL-1β levels were (23.93±14.82), (82.42±20.84), (69.46±22.23), (40.92±11.21) and (35.42±10.34) pg·mL^-1，respectively. The intestinal TNF-α levels were (101.60±11.18), (158.70±23.47), (146.40±17.90), (115.70±21.06) and (91.84±21.57) pg·mL^-1, and the intestinal IL-1β levels were (724.60±78.73), (1 043.00±106.32), (836.35±103.35), (774.60±133.68) and (694.50±40.84) pg·mL^-1，respectively. The relative expression levels of tight junction protein ZO-1 in colon tissue were 1.01±0.01, 0.48±0.01, 0.46±0.01, 0.61±0.09 and 1.15±0.10, and the relative expression levels of tight junction protein Occludin in colon tissue were 1.00±0.01, 0.64±0.11, 0.57±0.13, 0.73±0.10 and 1.02±0.13，respectively. The levels of TNF-α in liver tissues were (1 727.00±223.70), (2 008.00±220.40), (1 762.00±45.19), (1 723.00±49.45), and (1 680.00±103.10) pg·mg^-1, and the levels of IL-1β in liver tissues were (1 317.00±331.40), (2 158.00±730.90), (1 546.00±258.90), (1 806.00±523.40), and (1 121.00±84.62) pg·mg^-1. The MDA levels in liver tissues were (0.98±0.15), (1.51±0.29), (1.29±0.30), (1.15±0.12) and (1.06±0.21) nmol·mg^-1, the reduced glutathione (GSH) levels in liver tissues were (8.46±0.60), (5.84±0.49), (6.30±0.27), (7.48±0.50) and (8.07±0.60) μmol·gProt^-1, the glutathione peroxidase (GSH-PX) levels in liver tissues were (666.90±68.39), (481.00±19.16), (562.80±45.61), (620.20±12.13) and (658.80±18.11) U·mgProt^-1.The above indicators in the medium and high dose experimental groups were statistically significant compared with the model group (all P<0.05).

AS-IV can effectively improve intestinal and liver injury in rats with UC induced by TNBS. The mechanism may be related to repairing intestinal mucosal barrier, inhibiting inflammatory response and improving liver antioxidant function.